Better folder/namespace structure

Important to note:
1. Due ```HtmlElement``` presence in ```RepkaQA\PageObject\Elements``` version of ```PageFactory::getElementSelector``` method from ```TypifiedPageFactory``` class was moved up to ```PageFactory``` class as ```wrapElementSelector``` method.
2. If you already started to add content to ```Block```/```Element``` classes of ```RepkaQA\BEM``` namespace, then beware that they were moved into ```RepkaQA\BEM\Elements``` namespace in b01cfb8 commit.